I have a '97 850 (non-turbo)with 75,000 miles on it. I'm having problems with the vehicle in that it is blowing out black smoke on heavy acceleration. Once the black smoke comes out, I can stomp on it a second time and the exhaust is clear. Also, sometimes during idle, there is black smoke coming from the exhaust. I've replaced the plugs (they were real dirty), replaced air filter and flame trap (filthy). But the problem continues. It appears that the car is running "rich" and I don't have a clue as to how to fix that. My gas mileage is poor (12 to 13 miles to the gallon) and all my driving is on open road and highway. The vehicle was purchased by me from an estate sale and prior to me buying it, it sat for about 6-months and was hardly driven.

Can anyone point me in the right direction to troubleshoot this. My GMC Yukon XL gets better mileage than this thing does.


Thanks.